SCCM 2016: Selected critical care in the ED literature 2015

Here are the references to articles mentioned in my talk at the Society of Critical Care Medicine’s 45th Critical Care Congress on February 23rd 2016.

There is so much literature that pertains to resuscitation critical care in the emergency department, conveyed by many journals. Here is just a tiny fraction of what came out in 2015 that might influence care:

Note that they recommend apneic oxygenation techniques. The NODESAT approach has recently taken off in EM, with some observation studies suggesting a benefit, but RCT evidence is lacking.

Apneic oxygenation
Out of ICU apneic oxygenation studies:

Three airway registry studies, one from ED, one from a prehospital & retrieval medicine service, and one from all non-OR intubations, show differences in outcomes with the introduction of NODESAT. In Sakle’s ED study of 635 patients, first pass intubation success without hypoxemia was improved from 69% to 82.1%. In Wimalasena’s retrieval medicine study of 728 patients, desaturation rates decreased from 22.6% to 16.5%. Both sets of authors recommend randomized control trials in the ED population. In Dyett’s non-OR intubation study, in the cohort of patients without respiratory failure, nasal cannulae apnoeic oxygenation significantly reduced the incidence of hypoxaemia (0 out of 31 [0.0%] versus 10 out of 60 [16.7%].

The FELLOW trial randomised 150 adult patients being intubated on ICU to apneic oxygenation of 15 l/min oxygen via nasal cannulae, vs no apneic oxygenation, showing no difference in the primary outcome of lowest arterial oxygen saturation measured by continuous pulse oximetry (SpO2) between induction and two minutes after successful ETT placement. Weaknesses include this being a small study, and 46 patients were excluded which may have included some of the sickest patients most likely to benefit. About a third had BiPAP prior to intubation suggesting possible shunt physiology – a group unlikely to benefit from simple nasal cannula oxygen, and a significant number received BMV post induction, and therefore weren’t truly apneic. See comments at http://emcrit.org/podcasts/fellow-trial/

My take home message is that this safe, low cost intervention appears to be of benefit to patients without shunt physiology who do not continue to receive ventilation post induction, by prolonging apnoea time and allowing a great chance of first pass success without desaturation, but RCTs are needed.

Out of ICU apneic oxygenation studies:
Three airway registry studies, one from ED, one from a prehospital & retrieval medicine service, and one from all non-OR intubations, show differences in outcomes with the introduction of NODESAT. In Sakle’s ED study of 635 patients, first pass intubation success without hypoxemia was improved from 69% to 82.1%. In Wimalasena’s retrieval medicine study of 728 patients, desaturation rates decreased from 22.6% to 16.5%. Both sets of authors recommend randomized control trials in the ED population. In Dyett’s non-OR intubation study, in the cohort of patients without respiratory failure, nasal cannulae apnoeic oxygenation significantly reduced the incidence of hypoxaemia (0 out of 31 [0.0%] versus 10 out of 60 [16.7%].

My take home message is that this safe, low cost intervention appears to be of benefit to patients without shunt physiology who do not continue to receive ventilation post induction, by prolonging apnoea time and allowing a great chance of first pass success without desaturation, but RCTs are needed.

Preoxygenation
A volunteer study, randomising preoxygenation methods, used a primary outcome of single-breath exhalation end-tidal oxygen (eto2). They compared a non-rebreather mask with a BVM device with and without NC oxygen, and with a without a standarised leak. They found similar results to the Groombridge study – that NC added to BVM did not enhance etO2. However, when a leak was present, the NC helped. NC also seemed to enhance preoxygenation via NRBM in this study, moreso when a leak was present.

Another study compared anaesthetic circuit with a non-rebreather mask with a BVM device, and assessed the NRM and BVM with and without nasal cannulae, and also whether the addition of a PEEP valve to the BVM made a difference. This resulted in a comparison of seven different preoxygenation strategies. They found in these healthy volunteers that BVM was similar to the anaesthetic circuit, and no additional benefit was conferred by the addition of nasal cannulae. In fact, there was a slightly lower FeO2 when the NC were added to the BVM, which one might postulate to be due to a less effective mask seal.

So where are we with nasal cannula oxygen for RSI in the ED in the light of these studies?

For apneic oxygenation, one small study suggest it probably doesn’t contribute to less desaturation on the ICU in patients who are being bagged or receiving BiPAP around their intubation.
For preoxygenation, it does not improve denitrogenation beyond BVM in patients with healthy lungs, unless a significant leak is present, which it may help to compensate for.

When using the conventional digital palpation method, 13 of 35 anaesthetists (37%; 95% confidence interval, 21–55%) were able to locate the cricothyroid membrane successfully within 2 min, whereas the success rate was 29 of 35 (83%; 95% confidence inter- val, 66–93%) when the structured stepwise ultrasonography method was applied (P=0.0008, McNemar’s test). This was achieved in a median [range] of 18 [5–45] s for the 13 instances of successful identification by palpation and in 48 [26–112] s for the 29 instances of successful ultrasound-guided identification of the cricothyroid membrane.

The results show that after a short dedicated teaching program and using a structured approach, anaesthetists can obtain a significantly higher rate of successful identification of the cricothyroid membrane than when they use their standard method, palpation. However, it took 48 [26–112] seconds to do so, which indicates that this method should be applied before managing a difficult airway, and not once hypoxia is already present.

The cricothyroid membrane was accurately identified with digital palpation in only 39% (11/28) of obese compared with 71% (20/28) of non-obese patients (p = 0.03). Averaged only 5mm distance on obese group (up to 9.5mm) so technique is relevant (vertical versus horizontal incision). Importantly, they made sure the head and neck were in the same position between palpation and sonography.

Three methods compared: palpation, ‘four finger’ technique, and ‘neck crease’ method. All performed poorly compared with sonographic gold standard, with the best (palpation) still failing in 38% of patients.

Extensive literature review of all case reports of local tissue injury and extravasation from vasopressors. There were 204 local tissue injury events from peripheral administration of vasopressors, with an average duration of infusion of 55.9 hours (± 68.1), median time of 24 hours, and range of 0.08 to 528 hours. In most of these events (174/204, 85.3%), the infusion site was located distal to the antecubital or popliteal fossae. Most of the patients who experienced extravasation events had no long-term sequelae.